How can you have an afebrile febrile convulsion? Well, it turns out you can. It occurs as convulsions in children with an acute infective illness and no fever. Usually the illness is a gastroenteritis. It denotes a more benign form of convulsion, similar to a classic febrile convulsion.
A febrile convulsion is defined as a generalised seizure that occurs in children 6 months to 6 years. It can last for up to 15 minutes and the child should be back to normal within 60 minutes at the most. There has to be a fever, usually greater than 38 degrees celcius and the seizure tends to occur on the upstroke of the fever. The child should have no major co-morbidities and should be limited to one seizure per 24 hour period.
We don’t really need to do much for these children except look for the cause of the fever, which is usually viral. We need to exclude meningitis. The group that concerns us is the non or inadequately immunised children. This subgroup, especially when they are less than 6months, may need a lumbar puncture.
Afebrile Febrile Convulsions are known to occur in children with rotavirus gastroenteritis, with no electrolyte abnormality and no hypoglycaemia. The incidence varies from 2-6% in the literature (JChild Neurol, 2001) and although the exact aetiology is unknown it is thought that it may occur from a mild encephalitis from direct viral infection or enterotoxin.
It usually occurs in the first 3 days of the illness, but can occur at any time, the seizures are generalised and there may be more than one seizure. These patient will have a normal CSF if afebrile and look well, and although they may have an abnormal EEG initially, this normalises and they usually have a benign course.
Again lets remember that in the febrile convulsion, we need to be careful to determine where the fever is coming from. Those children less than 6 months old may need a lumbar puncture, those 6 to 12 months old, should probably have a lumbar puncture if they are not immunised, or they have been on a course of antibiotics, or they look unwell.